DE10214722A1 - Internal combustion engine regulator computes desired choke angle based on required air throughput rate (based on required torque) and desired induction pressure (based on desired air throughput rate) - Google Patents

Abstract

The regulator has a device for computing required indicated torque based on the gas pedal position and similar, a device for computing a required air throughput rate based on the required torque or similar and a device for computing the desired suction pressure based on the desired air throughput rate or similar. The desired choke angle is computed based on the required air throughput rate and the desired induction pressure The engine has a demand choke angle computation device (5) and a choke flap controller (6). The regulator has a device (1) for computing the required indicated torque to be produced by internal combustion engine combustion based on the gas pedal position and similar, a device (2) for computing a required air throughput rate based on the required torque or similar and a device (4) for computing the desired induction pressure based on the desired air throughput rate or similar. The desired choke angle is computed based on the required air throughput rate and the desired induction pressure.

Description

The present invention relates to a regulator for an internal combustion engine in which a so-called electronic Throttle system for electronic control of the throttle angle is mounted.

An internal combustion engine with an electronic Throttle system of this type is said to have high driveability Response behavior of an accelerator operation by the driver realize. JP-A-10-103116 discloses this following procedures. First, a required one Air flow rate (flow rate of the to an engine air to be supplied) using an intake system model is calculated and an actual intake pressure is given by a Intake pressure sensor detected. A target throttle angle is on the Basis of the required air flow rate and the actual Intake pressure is calculated and an engine is driven to cause an actual throttle angle with the target Throttle angle matches.

An air flow rate characteristic, which is determined by the throttle angle and the intake pressure, is shown in FIG. 6, for example. However, the characteristics of the products change depending on a combination of the components of a system, a combination of the parts, and the like. The changes are referred to as individual differences or product defects. Accordingly, as shown in FIG. 7, when, for example, a change is such that an air flow rate at a predetermined throttle angle is higher than a design value, the actual flow rate of the air flowing in an intake manifold becomes higher than a required air flow rate so that the actual -Suction pressure becomes higher than a suction pressure if there is no change. Increasing the intake pressure causes the exhaust gas recirculation flow rate (hereinafter referred to as an EGR flow rate) to decrease, so that a change in the actual intake pressure increases. As a result, a target throttle angle calculated using the actual intake pressure becomes larger than an ideal target throttle angle calculated using an intake pressure when there is no change. As a result, a viscous circle appears more and more, so that the actual air flow rate becomes higher than the required air flow rate. When the target throttle angle is calculated using the actual intake pressure, the target throttle angle in the direction of increasing the changes in the actual air flow rate is briefly calculated, and the viscous circle appears more and more, so that the control accuracy (the throttle control accuracy) the actual air flow rate is reduced compared to the required air flow rate.

A taxation procedure is also known, known as a Torque control is called. In the Torque demand control becomes an acceleration force (required braking torque) by the driver is determined by an accelerator pedal position determined by the driver is operated, the engine speed and the like and according to the acceleration force Cylinder air charge quantity (throttle angle), one Fuel injection amount, an ignition timing and the like controlled. Specifically, the required braking torque is in accordance with the driver's accelerator operation amount and the engine speed is calculated and the loss torque of the motor becomes that required braking torque is added, which the required displayed torque (Combustion pressure torque) is obtained. A target Cylinder air charge quantity (target intake air quantity) is according to the required torque displayed and a target Throttle angle is according to the target cylinder air charge amount calculated. The required braking torque is one Required value (setpoint) of a crankshaft  obtained net torque. The required displayed Torque is a required value (setpoint) of a Combustion pressure torque generated by the combustion in the Engine is generated. The loss torque is a torque by a loss of friction or the like in the engine is consumed and a load of external ancillaries. The required torque is shown by a sum of required braking torque and the loss torque expressed.

In the engine of a vehicle of the past few years Achieving improved fuel economy, one higher performance and reduced exhaust emissions variable valve timing system, an exhaust gas recirculation system and a fuel vapor gas treatment system and the like assembled. The variable valve timing system is also called designated a VVT. The fuel vapor gas treatment system is also referred to as a flushing system. The fuel vapor is also called a vapor and its flow rate is called a flush amount. Each of the systems is one Factor that causes fluctuations in the amount of cylinder air loaded. Hence there is a disadvantage that a Calculation accuracy of the target throttle angle itself deteriorates due to an influence of the variable Valve timing, an EGR flow rate, a purge rate and the like and accurate throttle control not can be carried out.

For example, when decelerating when a vehicle is going downhill drives or drives at high speed even if the Engine speed is in a high speed range, the required braking torque is reduced. If that required braking torque is reduced, a Throttle valve is closed and the air intake quantity is reduced. If the required braking torque is in the Reduced high speed range, therefore, an intake pressure drops (Intake manifold pressure) sharply. This can cause the  Intake pressure drops to 20 kPa, for example, and as a result Problems arise, such as that engine oil in the Cylinder is sucked in through the intake manifold, the Cylinder air charge quantity becomes insufficient and a Combustion state becomes unstable.

The invention has been accomplished in view of such circumstances and their job is therefore to improve one Air flow rate control accuracy. The Air flow rate control accuracy is also considered one Throttle control accuracy called.

Another feature of the invention is that Creation of a regulator for an internal combustion engine, the one Can calculate target throttle angle without increasing an error, even if a throttle angle / Air flow rate characteristic changes.

Another feature of the present invention is in the creation of a regulator for an internal combustion engine, the can prevent the occurrence of problems such as the increase in engine oil due to an extreme drop in engine oil Suction pressure.

To achieve the object, the controller for an internal combustion engine of the invention uses the configuration shown in FIG. 1.

The required displayed torque to be generated by the combustion of an internal combustion engine based on an accelerator pedal position operated by the driver and the like is calculated by the required displayed torque calculator 1 . On the basis of the required displayed torque or the like, a required air flow rate is calculated by the required air flow rate calculator 2, and on the basis of the required air flow rate or the like, a target suction pressure is calculated by the target suction pressure calculator 4 . The target throttle angle is calculated by the target throttle angle calculator 5 based on the required air flow rate and the target intake pressure. A control signal in accordance with the target throttle angle is output to the throttle valve driver 6 , and control is performed to establish the throttle angle in accordance with the target throttle angle.

The invention takes into account the fact that on the Based on the required air flow rate or the same target suction pressure calculated is not affected by changing the Throttle angle / air flow rate characteristics.

According to the target throttle angle is calculated by Use the target suction pressure and not an actual Suction pressure. Even if that Throttle angle / air flow rate characteristic changes The target throttle angle can consequently be increased without increasing the error be calculated and the Air flow rate control accuracy can be improved become.

When applying the invention to a system with a Exhaust gas recirculation control valve for controlling an exhaust gas recirculation amount and / or a variable valve timing mechanism for Changing the valve timing can be a configuration for Calculate the target intake pressure given the Exhaust gas recirculation quantity and / or the valve timing used become. Since in particular the engine control parameters as factors, that cause a change in suction pressure, not just that Air flow rate, but also the exhaust gas recirculation rate and the valve timing, can in the system with the Exhaust gas recirculation control valve and / or the variable Valve timing mechanism by calculating the target  Intake pressure in view of the exhaust gas recirculation quantity and / or Valve timing is the target intake pressure given a Amount of change in the intake pressure can be calculated, the is caused by the exhaust gas recirculation quantity and / or Valve timing. The calculation accuracy of the Target suction pressure can be improved.

If the amount of air that enters the cylinder one Internal combustion engine is sucked in, becomes too small Pressure in the cylinders too low, a phenomenon that that Engine oil rises and enters the cylinders through the pistons, occurs (which is referred to as a so-called oil rise phenomenon) and there is a possibility that the amount of oil consumed increases and the exhaust emissions deteriorate.

As a countermeasure against the problem, a configuration for calculating the target throttle angle by regulating the lower limit of the required air flow rate by the minimum air flow rate regulator 3 can be used. With the configuration, the lower limit of the required air flow rate can be regulated within the range in which the oil rise phenomenon does not occur. Even in the operating conditions that the required air flow rate is minimal, the occurrence of the oil increase phenomenon can be prevented, and the problems of increasing the oil consumption amount and deteriorating the exhaust gas emissions due to the oil increase phenomenon can be solved.

Calculated in another configuration of the invention the target cylinder air charge amount calculator a Target cylinder air charge quantity (target intake air quantity) on the Based on the required torque displayed or the like and a basic target suction pressure calculator calculates a basic target intake pressure based on the Target cylinder air charge quantity and the engine speed. A target Intake pressure correction device receives a target intake pressure  by correcting the basic target suction pressure in accordance with a given parameter as a factor that Fluctuations in suction pressure. A target Throttle angle calculation device calculates a target Throttle angle based on the target intake pressure and the Target cylinder air charge quantity and controls a throttle actuator based on the target throttle angle.

During configuration, the target throttle angle is on the Basis of the target suction pressure and the target Cylinder air loading quantity calculated. Compared to computing of the target throttle angle only from the target cylinder air charge quantity as with conventional technology, the Calculation accuracy of the target throttle angle improved become. In addition, the target intake pressure is determined by a Correction of the basic target suction pressure calculated, the calculated is based on the target cylinder air charge amount and the Engine speed in accordance with specified parameters as factors that cause fluctuations in intake pressure the target throttle angle can be calculated without by the parameters to be influenced. Even at Operating states that the intake pressure through the parameters fluctuates, accurate throttle control can be realized that meets the target cylinder air charge quantity.

It is also possible to increase the target cylinder air charge quantity correct that is calculated based on the required displayed torque or the like the target cylinder air charge amount correction device in Agreement with the parameters as factors that Cause fluctuations in the amount of cylinder air charge, and the Target throttle angle based on the corrected target To calculate the cylinder air charge quantity and the target intake pressure. In the configuration, the target cylinder air charge quantity can also corrected in a manner similar to the target intake pressure are in accordance with given parameters as Factors that cause fluctuations and  Control accuracy of the cylinder air charge amount can further be improved.

In doing so, parameters include as factors the fluctuations of the intake pressure and the cylinder air charge quantity, for example the EGR flow rate, the purge flow rate and atmospheric pressure. Since EGR gas and vaporization gas in the Intake manifold are inserted downstream of the throttle valve the EGR flow rate and the purge flow rate are one Interference air volume that does not pass through the throttle valve. However, the main components of the EGR gas are inactive Gas components so that the influence on the torque of the EGR Flow rate can be neglected. The EGR Flow rate can therefore be viewed as a factor which only causes fluctuations in intake pressure. On the other hand, evaporation gas is fresh air with high Hydrocarbon concentration from the container for the Adsorption of hydrocarbon components is introduced that evaporate from the fuel tank into the intake manifold and is intake fresh air that is not through one Intake air quantity sensor (air flow meter) is detected, the is arranged upstream of the throttle valve. That's why it is desirable to consider the purge flow rate as a factor consider the fluctuations of both the suction pressure as well the cylinder air charge quantity caused.

It is also possible to get the basic target intake pressure below Use at least the EGR flow rate and / or the Flushing flow rate as given parameters as factors correct the fluctuations in the suction pressure, and the target cylinder air charge amount using at least the Purging flow rate as a given parameter as a Correct factor of fluctuations in the Cylinder air charge caused. When configuring the basic target intake pressure and the target cylinder air charge quantity are corrected with high accuracy using  Main fluctuation factors from various fluctuation factors of the intake pressure and the cylinder air charge quantity.

In an internal combustion engine with the variable Valve control mechanism for changing the valve timing of a Intake valve and / or an exhaust valve changes Intake pressure according to the valve timing, so that the Basic target intake pressure after calculating the Basic target suction pressure can be corrected. The influence of Valve timing, which is exerted on the intake pressure, however, changes according to the engine speed and the Cylinder air charge amount. If the basic target suction pressure by the Valve timing is corrected, it is desirable that Relationships between valve timing, engine speed and to consider a cylinder air charge quantity.

The basic target suction pressure can be calculated on the Basis of the target cylinder air charge quantity, the engine speed and the valve timing. In the configuration the Basic target suction pressure can be obtained given the influence the valve timing. Thus the influence of Valve timing is eliminated and the calculation process of the target intake pressure in view of the influence of Valve timing is made easier.

If the intake pressure (intake manifold pressure) caused by the Intake pressure detection device is detected, equal to or lower than a predetermined target intake pressure lower limit the target intake pressure is set to the target Inlet pressure lower limit set by the Setup device for the lower limit and the target Cylinder air charge quantity can be set to the Cylinder air charge lower limit value can be set in Agreement with the target intake pressure lower limit. With the Configuration can, for example, even in operating states, such as the decrease in the required displayed Torque at high engine speed, such as the  Decelerate while driving downhill or while driving with high speed an extreme drop in suction pressure avoided become. Problems can thus be prevented, such as for example that the engine oil in the cylinders rises and enters the intake manifold or the amount of cylinder air becomes insufficient and the combustion state becomes unstable.

Furthermore, given a delay in appearance a change in the throttle angle (change in Throttle air flow rate) as a change in an actual Cylinder air loading quantity can be the target cylinder air loading quantity Phase advance compensation suspended by the amount of delay become. With the configuration, the influence of the Delay element of the air intake system are eliminated and the control accuracy of the cylinder air charge amount can be improved become.

When idling, the basic target intake pressure are calculated using the target idle speed as the engine speed. With the configuration the Basic target intake pressure set up so that the engine speed approaches the target idle speed so that the Idle speed stability can be improved.

The target throttle angle can also be calculated under Use of an inverse model of an intake system model of the Behavior of the intake air during a period since Change the throttle angle until the change appears as a change in an actual cylinder air charge amount. It means that the inverse model of the intake system model a model for Receiving the target suction pressure and the target Cylinder air charge quantity is and gives the throttle angle. Hence using the inverse model of the Intake system model can be a precise control of the Cylinder air charge amount can be realized based on the Target intake pressure and the target cylinder air charge quantity.  

Fig. 1 is a block diagram showing the configuration of a throttle control system of the invention.

Fig. 2 shows a configuration diagram of a control system for a direct injection type engine according to an embodiment of the invention.

Fig. 3 is a flowchart showing the flow processes of a throttle control program.

Fig. 4 is a block diagram showing a calculation model of a target throttle angle from a required air flow rate and the like.

Fig. 5 is a block diagram showing a calculation model of an EGR flow rate.

Fig. 6 is a graph of air flow rate characteristics which are determined by a throttle angle and an intake pressure.

Fig. 7 is a graph for explaining problems of a conventional technique.

Fig. 8 shows a configuration diagram of a control system for a direct injection type engine according to a second embodiment of the invention.

Fig. 9 is a block diagram showing a torque demand control of the direct injection engine.

FIG. 10A and 105 show block diagrams of the control modes a homogeneous combustion mode and a stratified charge combustion mode, respectively.

Fig. 11 is a block diagram showing a throttle control in the homogeneous combustion mode.

Fig. 12 shows a block diagram of the throttle control.

Fig. 13 shows a block diagram of the throttle control.

Fig. 14 shows a block diagram for calculating a Grundsollansaugdrucks Pmbase.

Fig. 15 shows a block diagram for calculating an atmospheric pressure correction factor FPO.

Fig. 16 shows a block diagram of the relationship between a Luftansaugsystemmodell and its inverse model.

Fig. 17 shows a block diagram of a throttle model.

Fig. 18 shows a block diagram of an inverse model of the Luftansaugsystemmodells.

Fig. 19 is a flowchart showing a throttle control program.

Fig. 20 is a flowchart showing the throttle control program.

An embodiment of the invention based on a Direct injection engine is applied below described with reference to the drawings.

First, a schematic configuration of an entire engine control system will be described with reference to FIG. 2. An air cleaner (not shown) is provided in the most upstream portion of an intake pipe 12 of an engine 11 as an internal combustion engine, and an air flow meter 13 for detecting an intake air amount is provided on the downstream side of the air cleaner. On the downstream side of the air flow meter 13 , a throttle valve 15 is provided, the angle of which is set by a motor 14 , such as a DC motor. The engine 14 matches the throttle drive device. The engine 14 is driven according to an output signal from an engine electronic control unit 16 (hereinafter referred to as an ECU) to thereby control the throttle angle of the throttle valve 15 , and an amount of air intake into each cylinder is adjusted by the throttle angle. A wind chamber 17 is provided downstream of the throttle valve 15 , and an intake pressure sensor 18 for detecting the intake pressure is attached to the wind chamber 17 . An intake manifold 19 for introducing air into each of the cylinders of the engine 11 is connected to the air chamber 17 , and a swirl control valve 20 for controlling a swirl in a cylinder of the engine 11 is provided in the intake manifold 19 of each cylinder.

A fuel injection valve 21 for injecting fuel directly into a cylinder is attached from an upper portion of each of the cylinders of the engine 11 . Fuel in a fuel tank 23 is brought to a high pressure with a fuel pump 23, and the pressurized fuel is supplied to the fuel injection valve 21 from each cylinder. The pressure of the fuel is detected by a fuel pressure sensor. In the cylinder head of the engine 11 , a spark plug 25 is attached to each cylinder, and an air-fuel mixture in the cylinder is ignited by sparking the spark plug 25 .

An intake valve 26 and an exhaust valve 27 of the engine 11 are driven by camshafts 28 and 29 , respectively, and the camshaft 28 on the intake side is provided with a hydraulic variable valve timing mechanism 30 for changing the timing of opening and closing the intake valve 26 in accordance with the operating conditions. The timing of opening and closing the intake valve 26 is referred to as a VVT advance value. Oil pressure for driving the variable valve timing mechanism 30 is controlled by an oil pressure control valve 31 . A crankshaft 33 is rotated by the reciprocating movement of a piston 32 from each of the cylinders of the engine 11 . By rotating the torque of the crankshaft 33 , ancillaries 34 (an air conditioner compressor, a generator, a torque converter, a steering assist device pump and the like) and a vehicle drive system are driven. A water temperature sensor 35 for detecting the cooling water temperature is attached to the cylinder block of the engine 11 .

On the other hand, an exhaust pipe 36 of the engine 11 is provided with a catalyst 37 such as a 3-way catalyst for treating the exhaust gas. An air-fuel ratio sensor 38 (or an oxygen sensor) for detecting the air-fuel ratio (or a rich / lean condition) of the exhaust gas is provided on the downstream side of the catalyst 37 . An EGR line 39 is connected between the upstream side of the air-fuel ratio sensor 38 and the wind chamber 17 in the exhaust line 36 for returning a part of the exhaust gas to the intake side. Approximately in the middle of the EGR line 39 , an EGR valve (exhaust gas recirculation valve) 40 is provided for controlling an exhaust gas recirculation flow rate (EGR flow rate).

The ECU 16 for controlling the engine operating conditions is mainly constructed by a microcomputer. By executing a throttle control program of FIG. 3 stored in a ROM (storage medium), the ECU 16 realizes the functions of a required torque calculation device 1 , a required air flow rate calculation device 2 , a minimum air flow rate regulator 3 , a calculation device 4 for a target intake pressure and a calculation device 5 for a target throttle angle, which is shown in FIG. 1.

The required displayed torque calculator 1 calculates a required displayed torque based on an output of an accelerator position sensor 41 for detecting the position of an accelerator or the like. The required displayed torque is a required value (target value) of an indicated torque, and the indicated torque is the torque generated by the combustion of the engine 11 , that is, the torque including an internal loss torque of the engine 11 and a loss torque due to the external load (load of the auxiliary units 34 ). Therefore, the torque obtained by subtracting the internal loss torque and the loss torque due to the external load from the indicated torque is the braking torque (net torque) obtained from the crankshaft 33 , and the vehicle drive system is driven by the braking torque.

The required displayed torque calculator 1 calculates a required braking torque Tdrv by a map or a numerical expression based on an output signal (accelerator pedal position) of the accelerator pedal position sensor 41 , the engine speed Ne, and the like. The required indicated torque Tind is obtained by adding different types of the loss torque Tloss (= internal loss torque + loss torque due to the external load) to the required braking torque Tdrv (Tind = Tdrv + Tloss).

The internal loss torque is a mechanical friction loss and a pump loss. The mechanical friction loss is calculated by a map or a numerical expression based on the engine speed Ne and the cooling water temperature THW, and the pump loss is calculated by a map or a numerical expression based on the engine speed Ne and the intake pressure Pm. The loss torque due to the external load is a load torque of the accessories 34 (an air conditioner compressor, a generator, a pump in a power steering device and the like) that is driven by the power of the engine 11 , and is calculated according to an air conditioner signal, a load current of the generator and the like.

When calculating the required displayed torque Tind can get the required indicated torque Tind are corrected by a Torque increase / decrease amount through a Idle speed control (ISC) or a loss and one load other than the above can be added. in the Contrast can be part of the internal loss and the external Load are disregarded for a calculation process simplify.

The required air flow rate calculating means 2 calculates a required air flow rate Gareq by a map or a numerical expression based on the required displayed torque Tind calculated by the required indicated torque and engine speed Ne calculating means 1 .

The minimum air flow rate regulator 3 calculates a minimum air flow rate Gamin, which is used to regulate the lower end value of the required air flow rate Gareq by the following equation.

Gamin = η × Vc × Pm × Ne / (120 × R × To)

η: charging efficiency
Vc: cylinder volume
Pm: intake air pressure
Ne: engine speed
R: gas constant
To: atmospheric temperature

The minimum air flow rate Gamin plays a role a lower limit to prevent the occurrence of a Oil rise phenomenon due to an extreme drop in pressure in a cylinder.

The minimum air flow rate regulator 3 compares the required air flow rate Gareq calculated by the required air flow rate calculation means 2 with the minimum air flow rate Gamin and selects a higher one of the required air flow rate Gareq and the minimum air flow rate Gamin than a final required air flow rate Gacylreq , This process is expressed as Gacylreq = max (Gareq, Gamin). Especially when Gareq Gamin applies, the process is carried out by Gacylreq = Gareq. If Gareq <Gamin, the process Gacylreq = Gamin is carried out. The process regulates the lower limit of the final required air flow rate Gacylreq at the minimum air flow rate Gamin.

The target suction pressure calculator 4 calculates a target suction pressure Pmtg by the following equation using the required air flow rate Gareq, an EGR flow rate Megr, an engine speed Ne, a volumetric efficiency ηvol, an atmospheric temperature To, a cylinder volume Vc, a gas constant R, and the like ( see Fig. 4).

Pmtg = (120 / Ne). (R.To/Vc).(1(/ηvol).(Gareq+Megr)

where (Gareq + Megr) denotes an air flow rate obtained by adding the EGR flow rate Megr to the required air flow rate Gareq and a flow rate corresponding to an air flow through the intake manifold 19 and into a cylinder. As shown in FIG. 5, the EGR flow rate Megr is calculated by the following equation using an EGR valve opening degree Θegr, an intake pressure Pm, an exhaust pressure Pe and an exhaust gas temperature Te.

Megr = g (Θegr) .Pe / √JTe.Φ (Pm / Pe)

where g (Θegr) denotes a flow rate property value calculated from a map of an EGR valve opening degree-EGR flow rate characteristic in accordance with the EGR valve opening degree Θegr. Φ (Pm / Pe) denotes a pressure property value calculated from a map or the like in accordance with the relationship between the suction pressure Pm and the outlet pressure Pe. In the system of FIG. 4, the suction pressure Pm is obtained by performing a first-order deceleration process on the target suction pressure Pmtg. A detection value (actual intake pressure) of the intake pressure sensor 18 can be used alternately. The volumetric efficiency ηvol is calculated from a map on the basis of the engine speed Ne and the intake pressure Pm. It is also possible to calculate the volumetric efficiency ηvol in view of the intake valve timing (VVT advance value).

On the other hand, the target throttle angle calculator 5 calculates a target throttle angle Tthtg based on the required air flow rate Gacylreq, the target intake pressure Pmtg, and the like as follows. First, based on the required air flow rate Gacylreq, the target suction pressure Pmtg, and the atmospheric pressure Po, an air flow rate property value f (Thr) is calculated by the following equation.

f (Thr) = Gacylreq.√To / Φ (Pmtg / Po) .Po

where Φ (Pmtg / Po) denotes a pressure property value, which is calculated from a map or the like in Agreement with the relationship between the target Intake pressure Pmtg and the atmospheric pressure Po.

Based on the air flow rate property value f (Thr) becomes the target throttle angle Tthtg by an inverse Property map one Throttle angle / air flow rate characteristic calculated.

The calculation process of the target throttle angle Thrtg by the above-described method is carried out by a throttle control program shown in FIG. 3. The program is executed by the ECU 16 at every predetermined time or crank angle. When the program is started, at step 101, the required braking torque Tdrv is first calculated by a map or a numerical expression based on the accelerator pedal position and the engine speed Ne. In view of other drive conditions, such as vehicle speed, the required braking torque Tdrv can be calculated.

In the following step 102 , the internal loss torque (mechanical friction loss and pump loss) and the loss torque due to the external load (load torque of an air conditioner compressor, a generator, a steering assist device pump, and the like) are calculated and summed, thereby obtaining the loss torque Tloss ,

Tloss = internal torque loss + torque loss Because of the external load.

Thereafter, the program proceeds to step 103 , where the loss torque Tloss is added to the required braking torque Tdrv, whereby the required indicated torque Tind is obtained.

Tind = Tdrv + Tloss

At step 104 , based on the required displayed torque Tind and the engine speed Ne, the required air flow rate Gareq is calculated by a map or a numerical expression. Then, in step 105, the volumetric efficiency ηvol is calculated from a map based on the engine speed Ne and the intake pressure Pm. The volumetric efficiency ηvol can be calculated in the same way in view of the intake valve timing (VVT advance value).

Thereafter, the program proceeds to step 106 , where the EGR flow rate Megr is calculated by the following equation using the EGR valve opening degree Θegr, the exhaust pressure Pe, the intake pressure Pm, and the exhaust gas temperature Te.

Megr = g (Θegr) .Pe / √Te.Φ (Pm / Pe)

The flow rate property value g (Θegr) becomes calculated from a map of the EGR valve opening degree / EGR Flow rate characteristics in accordance with the EGR Valve opening degree Θegr. The pressure property value Φ (Pm / Pe)  is calculated from a map or the like in Agreement with the relationship between the intake pressure Pm and the outlet pressure Pe.

The suction pressure Pm used in steps 105 and 106 can be obtained by performing a first-order deceleration process on the target suction pressure Pmtg or by using a detection value (actual suction pressure) of the suction pressure sensor 18 .

At the following step 107 , the target intake pressure Pmtg is calculated by the following equation using the required air flow rate Gareq, the EGR flow rate Megr, engine speed Ne, the volumetric efficiency ηvol, the atmospheric temperature To, the cylinder volume Vc, the gas constant R, and the like (see Fig. 4).

Pmtg = (120 / Ne). (R.To/Vc).(1/ηvol).(Gareq+Megr)

Thereafter, the program proceeds to step 108 , where the minimum air flow rate Gamin used to regulate the lower limit of the required air flow rate Gareq is calculated by the following equation using the engine speed Ne, the intake pressure Pm, the atmospheric temperature To and the volumetric efficiency ηvol.

Gamin = ηvol × Vc × Pm × Ne / (120 × R × To)

The required air flow rate Gareq calculated at step 104 is compared to the minimum air flow rate Gamin and the higher of the required air flow rate Gareq and the minimum air flow rate Gamin is chosen as the final required air flow rate Gacylreq. As a result, the lower limit of the final required air flow rate Gacylreq is regulated by the minimum air flow rate Gamin. This process is called a regulation process.

Thereafter, at step 109 , the target throttle angle Tthtg is calculated as follows based on the required air flow rate Gacylreq, the target intake pressure Pmtg, and the like. First, the air flow rate property value F (Thr) is calculated based on the required air flow rate Gacylreq, the target suction pressure Pmtg, and the atmospheric pressure Po. Then, based on the air flow rate property value F (Thr), the target throttle angle Tthtg is calculated by an inverse property map of the throttle angle / air flow rate characteristic.

In the following step 110 , a control signal according to the target throttle angle Tthtg is output to the engine 14 to control the throttle angle so that it matches the target throttle angle Tthtg.

In the previous embodiment, given the Fact that the actual intake pressure changes due to Changes in throttle angle / air flow rate characteristics changes caused by changes in the manufacture of the system and the like, and further in view the fact that the target intake pressure Pmtg that is on the Basis of the required air flow rate Gacylreq and the same is calculated, is not influenced by the Changes in throttle angle / air flow rate characteristics, when calculating the target throttle angle Tthtg, the target Throttle angle Tthtg using not the actual intake pressure but the target intake pressure Pmtg calculated. Even if that Throttle angle / air flow rate characteristic changes without increasing the error, the target throttle angle can consequently Tthtg can be calculated and the  Air flow rate control accuracy (throttle control accuracy) can be improved.

In addition, the EGR is in the embodiment Flow rate Megr in the arithmetic expression of the target Intake pressure Pmtg considering the fact that the EGR flow rate Megr a factor to change the Suction pressure is. As a result, the target suction pressure Pmtg are calculated in view of the change amount of the Suction pressure through the EGR flow rate Megr, so the Calculation accuracy of the target intake pressure Pmtg improved can be.

If the volumetric efficiency ηvol is calculated in view of the intake valve timing (VVT advance value) when calculating the volumetric efficiency ηvol, which in the arithmetic expression of the target intake pressure Pmtg included is, the target intake pressure Pmtg in view of the Amount of change in suction pressure by the Intake valve timings are calculated, and the Calculation accuracy of the target intake pressure Pmtg can continue be improved. In an engine with one Evaporative purging system for purging evaporative gas (Fuel vapor) adsorbed in a container into the Air intake system when the target intake pressure Pmtg in view of the flushing volume of the evaporation gas the target intake pressure Pmtg with high accuracy given the amount of change in suction pressure by the Purging the evaporation gas can be calculated.

If the amount of air sucked into the cylinders of the engine 11 becomes too small, the pressure in the cylinders becomes too low and there is a phenomenon that the engine oil rises and enters the cylinders through the pistons (oil increase phenomenon) and there is a possibility that the oil consumption amount increases and the exhaust gas emissions worsen.

As a countermeasure against the problem, the target Throttle angle Tthtg by regulating the lower limit of required air flow rate Gacylreq by the minimum Air flow rate Gamin calculated so that the lower one Limit of required air flow rate Gacylreq can be regulated within a range in which the Oil rise phenomenon does not occur. Even at Operating conditions, the required air flow rate Gacylreq is minimal, the occurrence of the Oil surge phenomenon can be prevented and problems one Increase in oil consumption and worsening of Exhaust emissions due to the oil rise phenomenon can be solved become.

A second embodiment of the application of the Invention on a direct injection engine described below with reference to the drawings.

First, a description will be made with reference to FIG. 8. The components that are the same or equivalent to those of FIG. 2 are given the same reference numerals and their description is not repeated. In FIG. 8, the components of the reference numerals 11-41 in Fig. 2 are shown. Fuel vapor (so-called evaporation gas), which is generated in the fuel tank 22 , is adsorbed in a container 43 via a line 42 . The container 43 is connected to the air tank 17 of the suction line 12 via a line 45 with a flushing control valve 44 . By controlling the position of the purge control valve 43 in accordance with the engine operating conditions, the flow rate of the evaporative gas (referred to as the purge flow rate) that is purged from the canister 43 and introduced into the air chamber 17 is controlled.

The ECU 16 , which controls the engine operating conditions, executes a torque demand control program, thereby performing the functions of the required displayed torque calculator 51 , the combustion mode switch means 52 , the homogeneous combustion mode controller 53, and the stratified charge combustion mode controller 54 as shown in FIG. 9. The functions are specifically described below.

The required displayed torque calculator 51 calculates the required displayed torque based on an output signal of the accelerator pedal position sensor 41 for detecting the position of an accelerator pedal (accelerator pedal position) or the like. The required displayed torque is a required value (target value) of an indicated torque, and the indicated torque is a torque generated by the combustion of the engine 11, that is, a torque including an internal loss torque of the engine 11 and a loss torque due to the external one Load (load of the auxiliary units 34 ). Therefore, the torque obtained by subtracting the internal loss torque and the torque due to external load from the indicated torque is the braking torque (net torque) obtained from the crankshaft 33 , and the vehicle drive system is driven by the braking torque.

The required displayed torque calculator 51 calculates the required braking torque based on an output signal (accelerator position) of the accelerator position sensor 41 , the engine speed Ne, the vehicle speed and the like, adds various types of the lost torque, which will be described later, to the required braking torque and corrects it the torque with an increase / decrease amount of the torque by an idle speed control (ISC), whereby the required indicated torque is obtained. The internal loss torque that needs to be added to the required braking torque is a mechanical friction loss and a pump loss. The mechanical friction loss is calculated by a map or a numerical expression based on the engine speed Ne and the cooling water temperature THW, and the pump loss is calculated by a map or a numerical expression based on the engine speed Ne and the intake pressure Pm. The loss torque due to the external load to be added to the required braking torque is a load torque of the accessories 34 (an air conditioner compressor, a generator, a power steering pump and the like) that are driven by the power of the engine 11 . and is set up according to an air conditioner signal, a load current of the generator, or the like. A correction torque (torque increase / decrease amount) by the ISC is calculated by a map or a numerical expression based on a target idle speed netarget and a current engine speed Ne.

When calculating the required displayed torque, a loss or load other than the internal loss and the external load shown in FIG. 2 may be added, or in contrast, part of the internal loss and the external load shown in FIG. 9 are neglected to simplify a calculation process.

The combustion mode switch 52 selects either the homogeneous combustion mode controller 53 or the stratified charge combustion mode controller 54 from a map or the like in accordance with the engine speed Ne and the required indicated torque, thereby switching the combustion mode. For example, in the low speed range and the low torque range, the stratified charge combustion mode controller 54 is selected and the operation is performed in the stratified charge combustion mode. In the stratified charge combustion mode drive, a small amount of fuel is injected directly into the cylinders on the compression stroke to produce a stratified charge air-fuel mixture, and stratified charge combustion is carried out, thereby improving fuel economy. In the middle and high speed range and the middle and high torque range, the controller 53 of the homogeneous combustion mode is selected and the operation is performed in the homogeneous combustion mode. In the homogeneous combustion mode drive, the fuel injection amount is increased, the fuel is injected directly into the cylinders on the intake stroke to produce a homogeneous air-fuel mixture, and homogeneous combustion is carried out, thereby increasing engine output and braking torque.

The functions of the homogeneous combustion mode controller 53 will now be described with reference to FIG. 10A. The homogeneous combustion mode controller 53 performs torque demand control with an air quantity priority that converts the required displayed torque into the target air quantity and establishes the target throttle angle. In view of the fact that the displayed torque fluctuates according to the ignition timing and the air-fuel ratio in the cylinders, the required displayed torque is corrected by the following equation using the ignition-timing efficiency (SA efficiency) and the air-fuel ratio efficiency (A / F ratio efficiency).

Required displayed torque after the correction Required indicated torque / (ignition timing efficiency × A / F ratio efficiency).

The ignition timing efficiency is established by a map or the like in accordance with an ignition delay. If the ignition delay is zero, the displayed torque is maximum. Accordingly, when the ignition delay is zero, the ignition timing efficiency is set to 1. The air-fuel ratio efficiency is established by a map or the like in accordance with the target air-fuel ratio. Based on the corrected required displayed torque and the engine speed Ne, a target cylinder air charge amount is calculated by a map or the like. Based on the target cylinder air charge amount, the engine speed Ne, the EGR flow rate, the VVT advance rate, the purge flow rate, and the like, the target throttle angle is calculated using a target throttle angle calculation model, which will be described below. A control signal according to the target throttle angle is output to the engine 14 of the electronic throttle system, and the throttle valve 15 is driven to control the throttle angle. The homogeneous combustion mode controller 53 calculates an estimated cylinder air charge amount from an output signal (throttle passage air amount) of the air flow meter 13 , the engine speed Ne, and an output signal (intake pressure Pm) of the intake pressure sensor 18 using a cylinder air charge amount estimation model. A target fuel amount is calculated by dividing the estimated cylinder air charge amount by the target air-fuel ratio. By multiplying the target fuel amount by various correction factors (cooling water temperature correction factor, air-fuel ratio feedback correction factor, learning correction factor and the like), the final fuel injection amount is obtained. An injection pulse having a pulse width in accordance with the fuel injection amount is supplied to the fuel injection valve 21 at the intake stroke of each cylinder to perform the fuel injection. When driving in the homogeneous combustion mode, the fuel is injected directly into the cylinders on the intake stroke to produce a homogeneous air-fuel mixture and homogeneous combustion is performed. Further, the homogeneous combustion mode controller 53 calculates the target EGR flow rate through a map or the like in accordance with the engine operating conditions and controls the EGR valve 40 in accordance with the calculation result to control the EGR flow rate to the target EGR flow rate. The homogeneous combustion mode controller 53 also calculates a target VVT advance value by a map or the like in accordance with the operating conditions, and controls the oil pressure control valve 31 of the variable valve timing mechanism 30 in accordance with the calculation result to make the VVT advance value the target VVT advance value Taxes. Further, the homogeneous combustion mode controller 53 calculates the ignition timing of each cylinder by a map or the like in accordance with the engine operating conditions and applies a high voltage to the spark plug 25 at the ignition timing to generate a spark output. From the ignition timing, the ignition timing efficiency calculation described above is calculated.

Referring now to FIG. 10B, the functions of the stratified charge combustion mode controller 54 will be described. The stratified charge combustion mode controller 54 performs torque demand control with a priority on the amount of fuel, which converts the required indicated torque into the target fuel amount, multiplies the target fuel amount by the target air-fuel ratio to obtain the target cylinder air charge amount, and the like Throttle angle sets up. In view of the fact that the displayed torque fluctuates according to the air-fuel ratio in a cylinder, the required displayed torque is corrected by being divided by the air-fuel ratio efficiency (required displayed torque after correction = required indicated torque-air-fuel ratio efficiency). According to the air-fuel ratio efficiency calculation method, in a similar manner to the homogeneous combustion mode controller 53, the air-fuel ratio efficiency is calculated by a map or the like in accordance with the target air-fuel ratio. Based on the corrected required displayed torque and the engine speed Ne, the target fuel amount is calculated by a map or the like. The target fuel amount is multiplied by various correction factors (cooling water temperature correction factor, air-fuel ratio feedback correction factor, learning correction factor, and the like), whereby a final fuel injection amount is obtained. An injection pulse having a pulse width in accordance with the fuel injection amount is output to the fuel injection valve 21 on the compression stroke of each cylinder to perform the fuel injection. In the stratified charge combustion mode, the fuel is injected directly into the cylinders on the compression stroke to produce a stratified charge air-fuel mixture, and the stratified charge combustion is performed. Furthermore, the stratified charge combustion mode controller 54 calculates the ignition timing by a map or the like in accordance with the target fuel amount and the engine speed Ne and applies a high voltage to the spark plug 25 at the ignition timing to generate a spark output. The stratified charge combustion mode controller 54 calculates a target cylinder air charge quantity by multiplying the target fuel quantity by the target air fuel ratio, calculates the target throttle angle based on the target cylinder charge air quantity, the engine speed Ne, the EGR flow rate, the VVT advance value, and the like, outputs a control signal according to the target throttle angle to the engine 14 of the electronic throttle system and controls the throttle valve 15 to control the throttle angle. The stratified charge combustion mode controller 54 drives and controls the EGR valve 40 in accordance with a target EGR flow rate that is established based on the target fuel amount or the like to control the EGR flow rate to the target EGR flow rate the oil pressure control valve 31 of the variable valve timing mechanism 30 in accordance with the target VVT advance value, which is established based on the target fuel amount and the like, to thereby control the VVT advance value to the target VVT advance value.

The configuration of the target throttle angle calculation model for calculating the target throttle angle based on the target cylinder air charge amount and the like in the homogeneous combustion mode drive will be described with reference to FIGS. 11 to 18. Fig. 11 shows a functional block diagram showing the sketch of the function in view of the throttle control of functions of the control device 53 of the homogeneous combustion mode. FIGS. 12 and 13 show functional block diagrams respectively showing a concrete example of the function in view of the throttle control. FIG. 14 shows a functional block diagram of the function of a calculation device 62 of a basic target suction pressure.

A cylinder air charge amount calculator 61 calculates the target cylinder air charge amount Metg through a map or the like based on the required displayed torque calculated by the required displayed torque calculator 51 and the engine speed Ne.

The target target intake pressure calculator 62 calculates a target target intake pressure Pmbase based on the target cylinder air charge amount Metg calculated by the target cylinder air charge amount calculator 61 , the engine speed Ne, and the VVT advance value as follows. In a steady drive mode, the relationships between the engine speed Ne, the target cylinder air charge amount Metg, and the intake pressure Pm are measured in advance for each lead value of the VVT. A map for calculating the basic target intake pressure Pmbase from the engine speed Ne and the target cylinder air charge amount Metg for each lead value of the VVT, as shown in FIG. 14, is generated and stored in the ROM of the ECU 16 . When calculating the basic target intake pressure Pmbase, a map is selected in accordance with the advance value of the VVT at the time, and the basic target intake pressure Pmbase is calculated from the engine speed Ne and the target cylinder air charge quantity Metg.

If the present VVT advance value does not match the VVT advance value of a group of maps stored in the ROM, two maps are selected which are closest to the present VVT advance value and the basic target intake pressure Pmbase is calculated by a linear interpolation. As shown in FIG. 14, the two basic target intake pressures Pmbase calculated from the two maps are approximated by a straight line, and the basic target intake pressure Pmbase according to the present VVT advance value is calculated from the straight line.

In the embodiment, the idle Basic target intake pressure Pmbase using the target Idle speed netarget instead of the actual engine speed Ne  calculated. In such a way when idling the Basic set pressure Pmbase set up so that the Engine speed Ne to the target idling speed netarget approximates so that the idle speed stability improves can be. According to the invention, however, the Basic target intake pressure Pmbase using the actual Engine speed Ne in a similar manner to one idle-free operation can be calculated.

A correction means 63 shown in Fig. 11 serves as a target suction pressure correction means for obtaining a target suction pressure Pmtg by correcting the basic target suction pressure Pmbase calculated by the basic target suction pressure calculation means 62 in accordance with predetermined parameters as factors that fluctuate of the intake pressure, and also serves as a target cylinder air charge amount correcting means for correcting the target cylinder air charge amount Metg in accordance with predetermined parameters as factors that cause fluctuations in the cylinder air charge amount.

In the exemplary embodiment, the EGR flow rate MEGR, the purge flow rate Mpurg and the atmospheric pressure Po are considered as predetermined parameters as factors which cause fluctuations in the suction pressure. As shown in Fig. 12, an EGR correction factor fEGR, a purge correction factor fpurg, and an atmospheric pressure correction factor fPo are calculated, and the basic target suction pressure Pmbase is corrected using the correction factors, thereby obtaining the target suction pressure Pmtg. When calculating the EGR correction factor fEGR, the EGR flow rate MEGR is first estimated by the estimator 59 for the EGR flow rate (see FIG. 11) based on the opening degree EGRV of the EGR valve 40 , the suction pressure Pm, the atmospheric pressure Po, the outside air temperature To and the like and the EGR correction factor fEGR is calculated using the EGR flow rate MEGR and the target cylinder air charge amount Metg.

fEGR = 1 + MEGR / Metg

When calculating the purge correction factor fpurg, the purge flow rate Mpurg is first estimated by the purge flow rate estimator 60 (see FIG. 11) based on the purge rate and the suction pressure Pm, and the purge correction factor fpurg is calculated by the following equation using the purge flow rate Mpurg and Target cylinder air charge quantity Metg.

fpurg = 1 + Mpurg / Metg

A calculation method of the atmospheric pressure correction factor fPo will now be described with reference to FIG. 15. The atmospheric pressure correction factor fPo is a correction factor with which the basic target intake pressure Pmbase and the target cylinder air charge quantity Metg can be calculated using a map that is measured in the state of driving at sea level or in a lowland region (standard atmospheric pressure Postd) even in an environment, in which the atmospheric pressure Po is lower than the standard atmospheric pressure Postd. The following relationship is satisfied in the steady drive mode when driving at sea level.

Mestd = Mthstd
= CAPostd / R√To.Φ (Pm / Postd) (1)

where Mestd is a cylinder air charge amount at sea level, Mthstd is a throttle passage air amount at sea level, and Postd is an atmospheric pressure at sea level or a standard atmospheric pressure. C denotes a flow coefficient, A denotes an effective throttle opening cross-sectional area, R denotes a gas constant and To denotes an outside air temperature. Φ (Pm / Postd) is calculated from a map or the like with characteristics as shown in FIG. 15.

The following relationship is fulfilled for the continuous drive operating mode while driving above sea level:

Mealt = Mthalt = CAPoalt / R√To.Φ (Pm / Poalt) (2)

where Mealt is a cylinder air charge amount above Is sea level, mthalt is a throttle passage air volume above sea level and Poalt is an atmospheric pressure above sea level. Φ (Pm / Poalt) is considered a so-called Print property value.

The following equation is derived from equations (1) and (2) above.

Mealt = Φ (Pm / Poalt) / Φ (Pm / Postd) .Poalt / Postd.Mestd (3)

Equation (3) indicates the relationship between the cylinder air charge amount Mestd at sea level and the cylinder air charge amount Mealt above sea level with respect to the same intake pressure Pm. From the relationship, the relationship between the target cylinder air charge amount Metgstd at sea level and a target cylinder air charge amount Metgalt above sea level with respect to the same suction pressure Pm is obtained as follows.

Metgalt = Φ (Pm / Poalt) / Φ (Pm / Postd) .Poalt / Postd.Metgstd
= fPo.Metgstd (4)

From the equation (4), the atmospheric pressure correction factor fPo is calculated by the following equation.

fPo = Φ (Pm / Poalt) / Φ (Pm / Postd) .Poalt / Postd (5)

Assuming that the atmospheric pressure Po detected by the atmospheric pressure sensor 46 matches the atmospheric pressure Poalt above sea level, the following equation is derived from the equation (6).

fPo = Φ (Pm / Po) / Φ (Pm / Postd) .Po / Postd (6)

In the equation (6), the atmospheric pressure Postd (standard atmospheric pressure) at sea level is a constant value, so that variables in the equation (6) are only the suction pressure Pm and the atmospheric pressure Po. The values that are detected by the intake pressure sensor 18 and the atmospheric pressure sensor 46 can be used as those values.

By multiplying the basic target suction pressure Pmbase by the EGR correction factor fEGR, the purge correction factor fpurg and the atmospheric pressure correction factor fPo, which are calculated as described above, the target suction pressure Pmtg is obtained.

Pmtg = Pmbase × fEGR × fpurg × fPo (7)

Regarding the atmospheric pressure correction factor fPo we will the calculation of the basic target intake pressure Pmbase the target Cylinder air charge quantity through the Atmospheric pressure correction factor fPo multiplied and is corrected by the atmospheric pressure correction factor fPo and the basic target intake pressure Pmbase can be calculated at Use of the corrected target cylinder air charge quantity Metg.

On the other hand, the setter 46 for the target intake pressure lower limit and the selector for the final target intake pressure are regulators for preventing the actual intake pressure Pm from dropping extremely. If the actual intake pressure Pm detected by the intake pressure sensor 18 is higher than a predetermined target intake pressure lower limit value Pmlimit, the final target intake pressure selector 65 selects the target intake pressure Pmtg calculated by the equation (7) as the final one Target intake pressure Pmtg.

In contrast, when the actual intake pressure Pm detected by the intake pressure sensor 18 is equal to or lower than the predetermined target intake pressure lower limit value Pmlimit, the selector 66 for the final target intake pressure selects the target intake pressure lower limit value Pmlimit that is set up by the device 64 for the Target intake pressure lower limit than the final target intake pressure Pmtg. The target intake pressure lower limit value Pmlimit is set to prevent an increase in engine oil into the cylinder and an insufficient amount of air (deterioration of the combustion state) caused by an extreme decrease in the intake pressure Pm.

The setting device 65 for the target cylinder air charge quantity lower limit and the selection device 67 for the final target cylinder air charge quantity are a regulating device for preventing an extreme decrease in the cylinder air charge quantity. The process is shown in Fig. 12. When the actual intake pressure Pm detected by the intake pressure sensor 18 becomes equal to or lower than the predetermined target intake pressure lower limit value Pmlimit, the final target cylinder air charge amount selector 67 selects a value as a final target cylinder air charge amount Metg obtained by correcting the target - Cylinder air charge quantity lower limit value Metglimit, which is set up by the device 65 for the target cylinder air load quantity lower limit value in accordance with the target intake pressure lower limit value Pmlimit with the purge flow rate Mpurg. The process is expressed as Metg = Metglimit - Mpurg.

In contrast, when the actual intake pressure Pm detected by the intake pressure sensor 18 is higher than the predetermined target intake pressure lower limit value Pmlimit, the selector 67 selects a value for the final target cylinder air charge amount as the final target cylinder air charge amount Metg, which is obtained by correcting the target Cylinder air loading quantity Metg, which is calculated by the calculation device 61 for the target cylinder air loading quantity with the purge flow rate Mpurg. The process is expressed as Metg = Metg - Mpurg.

On the other hand, the target throttle angle calculator 68 shown in FIG. 11 calculates a target throttle angle Thrcom based on the target intake pressure Pmtg and the target cylinder air charge amount Metg using a target throttle angle calculation model with a phase advance compensation, which will be described later a control signal according to the target throttle angle Thrcom to a throttle actuator (motor 14 ) and controls the throttle valve 15 to control the throttle angle to the target throttle angle Thrcom.

The target throttle angle calculation model with phase advance compensation used in the embodiment is derived from an air intake system model (a throttle model and an intake manifold model) as shown in FIG. 16 as follows.

The intake manifold model is a model of the behavior of intake air flowing through an intake tract extending from the throttle valve 15 to the intake port of the engine 11 (hereinafter referred to as an "intake tract downstream of the throttle") and is governed by the mass conservation law and a gas state equation derived as follows. When the mass conservation law is applied to the flow of the intake air in the intake path downstream of the throttle, the relationship expressed by the following equation (8) is obtained.

d / dt.Min = Mth - Me (8)

where d / dt.Min is a change amount of air mass in the Intake path designated downstream of the throttle, Mth one Throttle passage air quantity and Me denotes one Displays the cylinder air charge quantity. Each of the values d / dt.Min, Mth and Me denotes a value per unit of time (or a Sample interval).

When the gas state equation is applied to the intake path downstream of the throttle, the relationship expressed by the following equation (9) is obtained.

Me = ηvol. (Ne / 60) /2.Vc. (Min / Vim) (9)

ηvol: volumetric efficiency
Ne: engine speed (min ^-1 )
Vc: cylinder volume
Vim: volume of the intake path downstream of the throttle

The following equation (10) is derived from the above equations (8) and (9).

d / dt.Min = Mth - ηvol. (Ne / 60) /2.Vc. (Min / Vim)
= Mth - Min / τim (10)

where τim denotes a model time constant of the intake manifold model and is expressed by the following equation (11).

τim = 120.Vim / (η.Ne.Vc) (11)

When equation (10) is subjected to a Laplace transform, the following equation is obtained.

sMin = Mth - 1 / τim.Min
∴Mim = 1 / (s + 1 / τim) .Mth
= τim / (1 (τim.s) .Mth (12)

From the equations (9), (11) and (12), the intake manifold model equation is derived, which is expressed by the following equation (13).

Me = 1 / τim.Mim
= 1 / τim.τim / (1 + τim.s) .Mth
= 1 / (1 + τim.s) .Mth (13)

The intake manifold model expressed by the equation (13) is a model for calculating the cylinder air charge amount Me from the throttle air passage amount Mth. Therefore, when an inverse model of the intake manifold model is used, the throttle air passage amount Mth can be calculated from the cylinder air charge amount Me. The inverse model of the intake manifold model is derived from equation (13) as follows.

Mth = (1 + τim.s) Ms
= Me + τim.s.Me (14)

In the above equation, when a differential element obtained by inverse transforming a first-order lag element is approximated by phase advance compensation to prevent τim.s.Me from divergence, an inverse manifold model (inverse manifold model) is derived , which is expressed by the following equation (15).

Mth = Me + τim.αT.s / (1 + αT.s) .Me (15)

αT.s / (1 + αT.s) denotes a transition function of the Phasenvoreilausgleichs. α denotes a time constant and α is greater than 1 (α <1). T denotes a sample cycle.

Therefore, the inverse intake manifold model for calculating the target throttle air passage amount Mthtg from the target cylinder air charge amount Metg is expressed by the following expression.

Mthtg = Metg + τim.αT.s / (1 + αT.s) .Metg (16)

On the other hand, the throttle model is constructed as shown in FIG. 17. The throttle model is expressed by the following equation.

Meth = CAPo / R√To.Φo
= f (Thr) .Po / √To.Φo (17)

Mestd denotes a cylinder air charge quantity Elevation, Mthstd denotes a throttle air flow rate at sea level, C denotes a flow coefficient, A denotes an effective throttle opening cross-sectional area, R denotes a gas constant and To presses the Outside air temperature off. Po indicates an atmospheric pressure and Φo denotes a print property value. f (Thr) is considered a Throttle air passage amount property value denoted and f (Thr) = C.A.1 / R. The Throttle air passage amount property value f (Thr) is through a map or the like in accordance with the Throttle angle Thr calculated. The Throttle air flow passage property value f (Thr) becomes so set up the throttle air flow rate Mth increases as the throttle angle Thr increases. The Print property value Φo is indicated by a map or the like in accordance with the relationship between the Suction pressure Pm and the atmospheric pressure Po calculated and can theoretically can be calculated as follows.  

If Pm / Po <(2 / (κ + 1)) ^{κ / (κ-1)} , the pressure property value Φo becomes Φo = 2κ / (κ-1). ((Pm / Po) ^{2 / κ} - (Pm / Po) ^{(κ + 1) (κ-1)} ) ^1/2 calculated.

When Pm / Po ≦ (2 / (κ + 1)) ^{k / (k-1)} , the pressure property value Φo becomes Φo = 2κ / (κ-1). ((2 / (κ + 1)) ^{2 / (κ-1)} - (2 / (κ + 1)) ^{(κ + 1) / (κ-1)} ) ^1/2 calculated.

κ denotes a ratio of the specific heat

The throttle model expressed by the equation (17) is a model for calculating the throttle air passage amount Mth from the throttle angle Thr. Therefore, when an inverse model (inverse throttle model) of the throttle model is used, the throttle angle Thr can be calculated from the throttle air passage amount Mth. The inverse throttle model is derived from equation (17) as follows.

f (Thr) = √To / Po.1 / Φo.Meth (18)

∴Thr = f ^-1 (√To / Po.1 / Φo.Meth) (19)

Therefore, the inverse throttle model for calculating the target throttle angle Thrcom from the target throttle air passage amount Mthtg is expressed by the following equation.

Thrcom = f ^-1 (√To / Po.1 / Φo.Mthtg) (20)

The target is achieved by a combination of the equation (16) of the inverse intake manifold model for calculating the target throttle air passage quantity Mthtg from the target cylinder air charge quantity Metg and the equation (20) of the inverse throttle model for calculating the target throttle angle Thrcom from the target throttle air passage quantity Mthtg - Throttle angle calculation model for calculating the desired throttle angle Thrcom derived from the desired cylinder air charge quantity Metg. The configuration of the target throttle angle calculation model (an inverse model of the air intake system model) is shown by the block diagram of FIG. 18.

The process of calculating the target throttle angle Thrcom using the target throttle angle calculation model is carried out by the throttle control program shown in FIGS . 19 and 20. The program is executed by the ECU 16 at any given time or crank angle. When the program is started, at step 201, the target cylinder air charge amount Metg is first calculated by a map or the like based on the required displayed torque and the engine speed Ne. When idling, to improve the idle speed stability, the target cylinder air charge amount Metg can be calculated using the target idle speed Netarget instead of the actual engine speed Ne.

Thereafter, the program proceeds to step 202 , where the basic target intake pressure Pmbase is calculated based on the target cylinder air charge amount Metg, the engine speed Ne, and the VVT advance value. When idling to improve the idle speed stability, the basic target intake pressure Pmbase can be calculated using the target idle speed Netarget instead of the actual engine speed Ne.

Thereafter, the program proceeds to step 203 where the EGR flow rate MEGR is calculated based on the opening degree EGRV of the EGR valve 40 , the suction pressure Pm, the atmospheric pressure Po, the outside temperature To and the like, and the EGR correction factor fEGR is calculated by the following equation is calculated using the EGR flow rate MEGR and the target cylinder air charge amount Metg.

fEGR = 1 + MEGR / Metg

In the following step 204 , the purge flow rate Mpurg is calculated based on the purge rate and the suction pressure Pm, and the purge correction factor fpurg is calculated by the following equation using the purge flow rate Mpurg and the target cylinder air charge amount Metg.

fpurg = 1 + Mpurg / Metg

Further, at step 205, the atmospheric pressure correction factor fPo is calculated by the equation (6) using the atmospheric pressure Po detected by the atmospheric pressure sensor 46 .

Thereafter, the basic target intake pressure Pmbase is calculated in step 206 with the EGR correction factor fEGR, the purge correction factor fpurg and the atmospheric pressure correction factor fPo, whereby the target intake pressure Pmtg is obtained.

Pmtg = Pmbase × fEGR × fpurg × fPo

At step 207 , it is determined whether or not the intake pressure Pm detected by the intake pressure sensor 18 is equal to or lower than the predetermined target intake pressure lower limit value Pmlimit. The target intake pressure lower limit value Pmlimit is set so that the rise of the engine oil into the cylinders and the insufficient amount of air (deterioration of the combustion state) caused by an extreme drop in the intake pressure Pm can be prevented. The target intake pressure lower limit value Pmlimit may be a fixed value preset by trial, simulation or the like, or may be set by a map or the like in accordance with the operating conditions such as the target cylinder air charge amount Metg.

If it is determined in step 207 that the actual intake pressure Pm is equal to or lower than the target intake pressure lower limit value Pmlimit, the program proceeds to step 208 where the target intake pressure lower limit value Pmlimit is established as the final target intake pressure Pmtg.

Pmtg = Pmlimit

Thereafter, the program proceeds to step 209 , where the target cylinder air charge amount lower limit value Metglimit is calculated in accordance with the target intake pressure lower limit value Pmlimit, and in the following step 210 , the target cylinder air charge amount limit value Metglimit is set as the target cylinder air charge amount Metg.

Metg = metglimit

In contrast, when it is determined in step 207 that the actual intake pressure Pm is higher than the predetermined target intake pressure lower limit value Pmlimit, the target cylinder air charge amount Metg calculated in steps 201 and 206 and the target intake pressure Pmtg are used as they are.

After determining the target cylinder air charge amount Metg and the target suction pressure Pmtg as described above, the program proceeds to step 211 , where the target cylinder air charge amount Metg is corrected by the purge flow rate Mpurg, thereby obtaining the final target cylinder air charge amount Metg becomes.

Metg = Metg - Mpurg

Thereafter, the program proceeds to step 212 , where the target cylinder air charge amount Metg is subjected to phase advance compensation by using the inverse intake manifold model, whereby the target throttle air passage amount Mthtg is calculated.

In the following step 213 , the throttle air flow rate passage property value f (Thr) of the inverse throttle model is calculated by the following equation using the target throttle air flow passage amount Mthtg, the atmospheric pressure Po, the outside air temperature To, and the pressure property value Φo.

f (Thr) = √To / Po.1 / Φo.Mthtg

The pressure property value Φo can be replaced by a Map or the like using Pmtg / Po as a Parameters are calculated.

Then, the program proceeds to step 214 , where the target throttle angle Thrcom is calculated by a map or the like in accordance with the throttle air flow rate passage property value f (Thr). Thereafter, at step 215 , a control signal is output to the engine 14 according to the target throttle angle Thrcom, and the throttle angle is controlled to match the target throttle angle Thrcom.

In the previous embodiment, the target Throttle angle based on the target intake pressure and the Target cylinder air charge quantity calculated. Consequently, in Comparison with the conventional technology, whereby the target Throttle angle only calculated from the target cylinder air charge quantity the control accuracy of the cylinder air charge quantity be improved. In addition, the target intake pressure obtained by correcting the basic target suction pressure, which is calculated from the target cylinder air charge and the Engine speed in accordance with the given Parameters (such as the EGR flow rate, the  Purge flow rate and atmospheric pressure) as factors that Cause fluctuations in the suction pressure, so that the target Throttle angle without being influenced by the parameters can be calculated. Even with operating conditions that Cause fluctuations in suction pressure due to the parameters, can be achieved a precise throttle control that the target Cylinder air charge quantity met.

Furthermore, in the exemplary embodiment, the target Cylinder air charge amount based on the required Torque and the like is calculated in accordance corrected with the given parameters (such as the purge flow rate) as factors that fluctuate Cylinder air charge amount cause, and the target throttle angle is calculated based on the corrected target Cylinder air charge quantity and the target intake pressure. Hence can also with regard to the target cylinder air charge quantity to a similar one As with the target intake pressure, the influence of the factors the fluctuations are eliminated.

If the suction pressure in the embodiment (Intake manifold pressure) equal to or lower than the specified one Target intake pressure becomes lower limit, becomes the target intake pressure set to the target intake pressure lower limit and the The target cylinder air charge quantity is set to the target Cylinder air charge lower limit in accordance with the Target intake pressure lower limit set. Hence can for example in operating conditions, such as one Decrease in the required indicated torque at high Engine speed, such as deceleration while driving downhill or while driving at high Extreme drop in intake pressure can be avoided. This can prevent problems such as that engine oil rises into the cylinders and into the intake manifold occurs or the cylinder air charge quantity becomes insufficient and the combustion state becomes unstable.  

Furthermore, given the embodiment a delay in the appearance of a change in the Throttle angle (change in throttle air flow rate) as a change in an actual cylinder air charge quantity the target Cylinder air charge a phase advance compensation by the Delay amount suspended. Therefore an influence of a Delay element of the air intake system are eliminated and the control accuracy of the cylinder air charge amount can be improved become.

The invention can be used as a controller for an engine used of all systems or at least one system has one variable valve timing mechanism, one EGR system and an evaporative flushing system. The invention can can also be applied to an engine with Intake duct injection with the electronic throttle system and the like and can be modified in various ways become.

A required displayed torque calculator ( 1 ) calculates the required displayed torque to be generated by the combustion of an internal combustion engine based on an accelerator pedal position or the like operated by the driver. A required air flow rate calculator calculates a required air flow rate based on the required displayed torque or the like. A target intake pressure calculator ( 4 ) calculates a target intake pressure based on the required air flow rate or the like. A regulating device ( 3 ) for a minimum air flow rate regulates the required air flow rate to a predetermined lower limit. A target throttle angle calculating means ( 5 ) calculates a target throttle angle based on the required air flow rate and the target intake pressure. A drive device ( 6 ) for the throttle valve drives a throttle valve in order to set up that an actual throttle angle matches the target throttle 00408 00070 552 001000280000000200012000285910029700040 0002010214722 00004 00289elwinkel. Even when properties between a throttle angle and an air flow rate change among products due to manufacturing changes in the systems or the like, the target throttle angle can be calculated with high accuracy.

Claims (11)

1. Regulator for an internal combustion engine with:
a target throttle angle calculation device ( 5 ) for calculating a target throttle angle; and
a throttle valve control device ( 6 ) for controlling a throttle valve on the basis of the desired throttle angle,
the controller has the following:
a required displayed torque calculating means ( 1 ) for calculating a required displayed torque to be generated by the combustion of the internal combustion engine based on a driver's accelerator pedal position and the like;
required air flow rate calculating means ( 2 ) for calculating a required air flow rate based on the required displayed torque or the like; and
a target suction pressure calculating means ( 4 ) for calculating a target suction pressure based on the required air flow rate or the like,
wherein the target throttle angle calculating means ( 5 ) calculates the target throttle angle based on the required air flow rate and the target intake pressure. 2. The controller for an internal combustion engine of claim 1, further comprising:
an exhaust gas recirculation control valve ( 40 ) for controlling an exhaust gas recirculation amount and / or a variable valve timing mechanism ( 30 , 31 ) for changing valve timing,
wherein the calculation device ( 4 ) for the target intake pressure calculates the target intake pressure in view of the exhaust gas recirculation quantity and / or the valve timing. 3. The controller for an internal combustion engine according to claim 1 or 2, further comprising a regulating device ( 3 ) for a minimum air flow rate for regulating a lower limit of the required air flow rate. 4. Regulator for an internal combustion engine with a throttle actuator ( 14 ) for driving a throttle valve, for calculating a required indicated torque, which is to be generated by the combustion of the internal combustion engine on the basis of an accelerator pedal position or the like actuated by the driver, calculating a target throttle angle based on the calculated required displayed torque or the like and controlling the throttle actuator based on the calculated target throttle angle with:
target cylinder air charge amount calculating means ( 61 ) for calculating a target cylinder air charge amount based on the required displayed torque or the like;
basic target intake pressure calculating means ( 62 ) for calculating a basic target intake pressure based on the target cylinder air charge amount and the engine speed;
target intake pressure correcting means ( 63 ) for obtaining a target intake pressure by correcting the basic target intake pressure in accordance with a predetermined parameter as a factor causing fluctuations in the intake pressure; and
a target throttle angle calculating means ( 68 ) for calculating a target throttle angle based on the target intake pressure and the target cylinder air charge amount. 5. The controller for an internal combustion engine of claim 4, further comprising:
target cylinder air charge amount correcting means ( 67 ) for correcting the target cylinder air charge amount calculated by the target cylinder air charge amount calculating means ( 61 ) in accordance with a predetermined parameter as a factor causing fluctuations in a cylinder air charge amount,
wherein the target throttle angle calculating means ( 68 ) calculates a target throttle angle based on the target cylinder air charge amount corrected by the target cylinder air charge amount correcting means and the target intake pressure. 6. Regulator for an internal combustion engine according to claim 5,
wherein the target suction pressure correcting means ( 63 ) corrects the basic target suction pressure by using at least an exhaust gas recirculation flow rate ( 59 ) and / or a purge flow rate ( 60 ) as predetermined parameters as factors causing fluctuations in the suction pressure, and
wherein the target cylinder air charge amount correcting means ( 67 ) corrects the target cylinder air charge amount by using at least the purge flow rate ( 60 ) as a predetermined parameter as a factor causing fluctuations in the cylinder air charge amount. 7. Controller for an internal combustion engine according to one of claims 4 to 6, further comprising:
a variable valve timing mechanism ( 30 , 31 ) for changing valve timing of an intake valve and / or an exhaust valve,
wherein the target target intake pressure calculating means ( 62 ) calculates a target target intake pressure based on the target cylinder air charge amount, the engine speed and the valve timing. 8. Controller for an internal combustion engine according to one of claims 4 to 7 with:
intake pressure detecting means ( 18 ) for detecting an intake pressure;
setting means ( 65 ) for setting a lower limit when an intake pressure detected by the intake pressure detection means becomes equal to or lower than a predetermined target intake pressure lower limit for setting the target intake pressure to the target intake pressure lower limit and setting the target cylinder air charge amount to the target cylinder air charge amount lower limit in accordance with the target intake pressure lower limit. 9. Controller for an internal combustion engine according to one of claims 4 to 8, further comprising:
phase advance compensation means ( 67 ) for performing phase advance compensation on the target cylinder air charge amount used by the target throttle angle calculator only by a delay amount in response to a delay in the appearance of a change in the throttle angle as a change in the actual cylinder air charge amount. 10. An internal combustion engine controller according to any one of claims 4 to 9, wherein the basic target suction pressure calculating means ( 62 ) calculates a basic target suction pressure by using a target idle speed as the engine speed in the idle state. 11. An internal combustion engine controller according to any one of claims 4 to 10, wherein the target throttle angle calculating means ( 68 ) calculates a target throttle angle by using an inverse model of an intake system model of intake air behavior during a period since a throttle angle was changed to the change appears as a change in the actual cylinder air charge quantity.